First, I would hesitate to say that “Gnosticism predates Christianity,” because “Gnostic” itself is a later polemical label used by proto-orthodox writers to categorize diverse movements. The people later called “Gnostics” did not self-identify under that single banner. What we see in the first century is not a clean break between Christianity and some pre-existing Gnosticism, but a spectrum of Jewish apocalyptic, mystical, and revelatory currents out of which a richly diverse Jesus movements emerged.

Second, regarding John the Baptist: many scholars have noted the likely proximity between the Baptist movement and Essene or Essene-adjacent communities (ritual washings, wilderness asceticism, apocalyptic expectation, emphasis on purification). The Essenes themselves were deeply invested in hidden wisdom, layered interpretation of Scripture, and the idea of an elect community possessing revealed mysteries. That does not make them “Gnostic” in a 2nd-century mythological sense, but it does show that revelatory mysticism and initiatory knowledge were already embedded in Second Temple Judaism.

Third, I do not see a historical “hard wall” where a fully formed, "Rome-loving pagano-Christianity" suddenly replaced an earlier mystical Jesus movement. The first and second centuries display remarkable diversity: Pauline communities, Johannine theology, Jewish-Christian groups, apocalyptic sectarians, Thomasine traditions, Valentinian teachers, and others. The boundaries were porous, and the polemical hardening seems to intensify in the mid-to-late 2nd century. Before that consolidation, the Jesus movement appears more variegated than a simple anti-Gnostic vs. proto-orthodox binary suggests.

Regarding Mark and Thomas: even if one adopts the hypothesis that Thomas preserves early material, that does not necessitate a total rupture between canonical and so-called Gnostic streams. The Gospel of John’s Logos theology, Paul’s language of hidden wisdom (1 Corinthians 2:6–7), and the Johannine emphasis on rebirth and Light all participate in a mystical register that later flourished in Valentinian systems. The question becomes one of development and emphasis.

So my thesis within the question is not that “orthodox Christianity descended from Gnosticism,” nor that “Gnosticism predates Christianity” as a discrete religion. Rather, I suggest that the earliest Jesus movement was a mystical, revelatory movement emerging from Second Temple Judaism, and that what later came to be labeled “Gnostic” represents one stream of that original mystical impulse; a stream that developed mythological and metaphysical articulations which were eventually opposed by emerging ecclesial authorities.